This invention relates to a motor vehicle with an internal combustion engine and a fuel cell.
Specifically, this invention relates to a motor vehicle comprising a hybrid drive device with an internal combustion engine and with at least one electric machine, at least one electric energy storage mechanism and one fuel cell system for supplying electricity.
Furthermore, this invention relates to a method for operating such a motor vehicle.
A motor vehicle and a method of this type are known from German Patent DE 199 13 794 A1 (Corresponding to U.S. Pat. No. 6,276,473). The known motor vehicle has an internal combustion engine which can drive the motor vehicle immediately after starting the vehicle electric system and an electric motor as the main drive motor which receives its power from a fuel cell system. The motor vehicle is driven by the electric motor instead of the internal combustion engine as soon as the fuel cell system has reached operating temperature due to heating of the exhaust gas of the internal combustion engine. After the fuel cell system has reached the operating temperature, the motor vehicle can be driven by the electric motor and/or by the internal combustion engine. From the power generated by the fuel cell system, secondary units of the motor vehicle and units of the fuel cell system can be supplied with the electric power which is needed to operate the at least one fuel cell of the fuel cell system.
WO 98/40922 describes a motor vehicle having a hybrid power generating system comprising a fuel cell system and an internal combustion engine. Hydrocarbon fuel is first cleaved in a pyrolysis reactor to form a fuel component containing hydrogen and the remaining fuel. The at least one fuel cell of the fuel cell system is operated with the hydrogen-containing fraction, supplying electric power for the electric motor. The remaining fuel may be used as fuel for the internal combustion engine. The fuel cell system is designed to supply approx. 50% of the max. power to be supplied by the hybrid vehicle. In a low-load range, the fuel cell system supplies all or most of the required power. At a higher load, the internal combustion engine is also operated. The internal combustion engine can be used directly for driving the vehicle wheels or for driving an electric generator which generates power for a single electric motor.
This invention is intended to achieve the object of reducing the power consumption of a motor vehicle by using a fuel cell system. This object is achieved according to this invention by a motor vehicle having an internal combustion engine, at least one electric machine, at least one electric energy storage mechanism; and a fuel cell system for generating electric power, and by a method for operating the same.
Accordingly, this object is achieved by the fact that the fuel cell system is designed as an auxiliary power source for delivering a lower power than the internal combustion engine; a control device is provided so that in its activated state, the fuel cell system can be operated continuously in a predetermined operating range or at a predetermined operating point of high efficiency, whereby the power it can deliver can be supplied to at least one power consuming device, and any excess power generated by the fuel cell system can be supplied to at least one additional power consuming device to obtain the high power delivery by the fuel cell system as required to achieve the high efficiency mentioned above. Therefore, the fuel cell system forms an auxiliary power unit.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.